The present invention relates to an apparatus for sensing sudden approach of one vehicle to another and emitting an alarm representative of such approach.
At a street intersection or the like, there occasionally occurs a careless sudden approach of one vehicle to another. A preceding vehicle at a halt thus may be approached by a succeeding vehicle due to careless driving. An accident is preventable if an alarm can be emitted to a driver by sensing such sudden approach.
Of the conventional approach sensing apparatus known heretofore, a type utilizing ultrasonic waves is considered advantageous in view of its relatively simple structure and high antinoise characteristic. However, since some ultrasonic component is included in the noise generated from a cooling fan and so forth of a vehicle engine, a problem arises in the sensing apparatus. Thus when any vehicle running at a normal speed has approached and stopped in the proximity of the apparatus-installed vehicle, malfunction may be induced by sensing the approach due to such noise from the cooling fan and so forth.